1. Field of the Invention
The present invention relates to a vehicle including a traction control device that prevents slippage of a driving wheel.
The present application claims priority from Japanese Patent Application No. 2012-178448, filed on Aug. 10, 2012, which is incorporated by reference herein in its entirety.
2. Description of the Related Art
Conventionally, as described in, for example, JP H07-103009, a vehicle including a traction control device is known. When a driving wheel slips at the time of starting or changing a gear of the vehicle, the traction control device decreases an output of an engine to suppress the slip.
Also conventionally, a vehicle including an automatic clutch which is automatically engaged or disengaged without being operated by a rider is known. Known automatic clutches include, for example, a centrifugal clutch which is engaged or disengaged in accordance with a rotation speed of the engine and a clutch which is engaged or disengaged by an actuator such as an electric motor or the like.
FIG. 7 is an example of a timing diagram obtained in the case where a vehicle including a traction control device described in JP H07-103009 also includes an automatic clutch and is subjected to traction control. In this example, the clutch is engaged or disengaged in accordance with the rotation speed (number of rotations per unit time; see reference character c2 in FIG. 7) of the engine. Therefore, at the time of starting or changing a gear of the vehicle, the clutch is put into a half clutch state from a disengaged state in accordance with an increase of the rotation speed of the engine (see arrow X1 in FIG. 7). When, at this point, the driving wheel slips with respect to a road surface (see arrows X2 in FIG. 7), the traction control device performs control to decrease the output of the engine in order to suppress the slip (see arrow X3 in FIG. 7). As a result, the rotation speed of the engine is decreased (see arrow X4 in FIG. 7), and therefore the clutch is shifted toward a position at which the clutch is disengaged (hereinafter referred to as a “disengagement position”; see arrow X5 in FIG. 7). As a result of the clutch being shifted toward the disengagement position, a torque conveyed from the engine to the driving wheel is decreased. Therefore, the amount of slip of the driving wheel (see reference character d3 in FIG. 7) is decreased (see arrow X6 in FIG. 7). When the amount of slip of the driving wheel is decreased, the traction control device increases the output of the engine (see arrow X7 in FIG. 7) and increases the rotation speed of the engine (see arrow X8 in FIG. 7). When, at this point, the clutch is shifted toward a position at which the clutch is engaged (hereinafter, referred to as an “engagement position”; see arrow X9 in FIG. 7) as a result of the increase of the output of the engine, the torque conveyed to the driving wheel is increased. Therefore, the driving wheel may slip again. As a result of the above-described series of operations being repeated, vibration is generated based on hunting of the clutch position, and thus the comfort of riding is lowered. In FIG. 7, reference character a1 represents an accelerator opening, reference character c1 represents a rotation speed of a main shaft, and reference character c3 represents a difference between the rotation speed of the engine and the rotation speed of the main shaft. Reference character d1 represents the rotation speed of the driving wheel, and reference character d2 represents a rotation speed of a subordinate wheel.